Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 2/29/2004
Publication Date: 2/1/2005
Citation: Jia, Y., Singh, P., Winston, E.M., Wamashe, Y., Correll, J., Lee, F.N., Moldenhauaer, K., Gibbons, J., Rutger, J.N. 2005. Development of molecular strategies to control major rice fungal diseases in the US [abstract]. Rice Technical Working Group Meeting Proceedings. Abstract p. 109.
Technical Abstract: Blast disease caused by the hemibiotrophic Magnaporthe grisea pathogen and sheath blight disease caused by the necrotrophic Rhizoctonia solani pathogen are serious diseases for U.S. rice industry. Common strategies for disease control are the use of resistant cultivars and pesticides in integrated pest management. Over the years, major resistance genes to blast have been identified from landrace cultivars and wild relatives of rice for blast control. Recent molecular characterization of two major blast resistance genes has facilitated the development of molecular markers from resistance genes for marker-assisted selection. In contrast, complete resistance source to sheath blight is not available in cultivated rice, and minor resistance genes have been used for sheath blight control. The current effort of the Molecular Plant Pathology program at Dale Bumpers National Rice Research Center is to explore the basic knowledge of rice natural defense for accelerating breeding for disease resistance. First, a major blast resistance gene Pi-ta, was determined to be responsible for preventing the infections of the most common blast races in the Southern US, and functional characterization of Pi-ta interacting genes will eventually lead to novel knowledge for sustained blast control. Secondly, robust pathogenicity assays for blast and sheath blight were developed to facilitate resistance gene identification and incorporation. Thirdly, molecular interactions of rice with the necrotrophic pathogen R. solani have been studied and several candidate genes were identified as an initial step to reach complete resistance to sheath blight. Fourthly, a lesion mimic mutant of the US rice cultivar Katy with enhanced resistance was recovered and a single recessive gene is responsible for this enhanced resistance to both M. grisea and R. solani. Fifthly, putative mutant populations of 20,000 M2 rice lines were developed for identifying resistance genes and resistance related genes using methods of both forward and reverse genetics. Finally, molecular mechanisms of the instability of rice blast fungus are better understood for predicting the stability of resistance in rice cultivars that are currently grown in the Southern US. In summary, new knowledge derived from this program has not only facilitated the development of end-user-friendly DNA markers for improved resistance but also generated useful genetic stocks that can be used for both basic and applied research for the rice community. In the future, public databases will be explored to develop molecular strategies for developing disease resistant rice cultivars. Increased use of resistant cultivars and decreased use of pesticides can facilitate the creation of an environmental friendly rice production system.